This invention is related generally to magnetrons and plasma processes, and more specifically to an application of such processes to sputter thin films of material on substrates.
There are a number of processes in various applications that involve plasma generation. An example is a dry etching process used in the fabrication of semiconductor circuits and elsewhere. Another example is the deposition of thin films onto substrates, also used in semiconductor circuit fabrication and elsewhere. A commercially important coating process uses a large magnetron to deposit thin films on large substrates such as building or auto glass wherein several layers of material are deposited in order to define certain optical characteristics of the substrate.
In this and other magnetron applications, it is highly desirable to be able to maintain control of a distribution of ions within the plasma since the ultimate product, whether from an etching, sputtering or other plasma process, is affected by this distribution. In the sputtering of thin films on large substrates, variations in the plasma density across the target cause corresponding variations in the rate of material deposition onto the substrate. Since most such applications require the deposited film to have the same thickness over the entire substrate, within a very small tolerance, other measures are taken to compensate for some non-uniformity of the plasma density but they are not always as effective as desired. Further, the plasma density profile across the target often changes during a thin film deposition or other plasma assisted process.
Therefore, it is a specific object of the present invention to provide techniques for controlling the plasma in a magnetron used for depositing films on substrates in order to result in the deposited films having uniform thickness.
It is another object of present invention provide techniques for controlling the plasma during the process of sputtering a dielectric film onto a substrate.
It is a more general object of the present invention to provide techniques for improving the level of control of various plasma processes.